Metal bipolar plate forming device and method

Abstract

The invention provides a metal bipolar plate forming device and method, and solves the technical problem that a material of an existing metal bipolar plate is subjected to severe plastic deformation in the die forming process, and local fracture is easily caused. The forming device is provided with a force transmission mechanism, the force transmission mechanism is provided with a force transmission plate, a force transmission rod and an edge pressing plate, and the force transmission plate is arranged between the upper die bottom plate and the upper die plate; the upper die bottom plate is connected with the force transfer plate through a hydraulic spring; the upper surface of the force transmission plate is connected with an ejector rod, the upper end of the ejector rod penetrates through the force transmission plate and extends out, and the force transmission plate is slidably connected with the ejector rod. One end of the dowel bar is connected with the dowel plate, the other end of the dowel bar downwards penetrates through the second through hole of the upper die plate and extends out to be connected with the edge pressing plate, the upper die plate is in sliding connection with the dowel bar, and the edge pressing plate is arranged above the lower die plate; the invention can be widely applied to the technical field of metal bipolar plates.

Description

Technical Field

[0001] The present application relates to the technical field of metal bipolar plates, and in particular to a metal bipolar plate forming device and method. Background Art

[0002] As an efficient and clean energy conversion device, fuel cells have broad application prospects in transportation, distributed energy, and portable devices. Metal bipolar plates are one of the core components of fuel cells. Their main functions include supporting the distribution of fuel and oxidant, conducting current, and providing mechanical support. Compared with traditional graphite bipolar plates, metal bipolar plates have higher mechanical strength, electrical conductivity, and thermal conductivity, and can significantly reduce thickness, thereby increasing the power density of the battery.

[0003] Metal bipolar plates need to have complex flow field structures to achieve efficient gas distribution and water management. Figure 1 As shown, a single microchannel of the bipolar plate is divided into five areas, namely the flange area, the upper fillet area, the side wall area, the lower fillet area, and the bottom area; the connection between the upper fillet area and the lower fillet area is set as area A, and the connection between the lower fillet area and the side wall area is set as area B.

[0004] In the common molding process, the thickness of the microchannel cross-section surface in the bipolar plate is obviously unevenly distributed; Figure 2 As shown in the figure, the thickness reduction rate of the A and B areas of the bipolar plate microchannels can usually reach 20%-30%; the sidewall area also undergoes large deformation, and the thickness reduction rate of the sidewall area is in the range of 15%-20%; the flange area and the bottom area only undergo small deformation, and the thickness reduction rate is about 5%. Therefore, the A and B areas of the bipolar plate microchannels are the main deformation areas, and their thickness reduction is serious. Severe thickness reduction means that the material undergoes severe plastic deformation during the forming process, which can easily lead to local rupture, especially for the A and B areas of the bipolar plate microchannels, which reduces the service life and mechanical support stiffness of the metal bipolar plate. Summary of the invention

[0005] The purpose of the invention is to solve the deficiencies of the above-mentioned technology and provide a metal bipolar plate forming device and method to improve the uniformity of the thickness of the entire microchannel of the metal bipolar plate and avoid the occurrence of rupture.

[0006] To this end, the invention provides a metal bipolar plate forming device, the forming device is provided with an upper mold mechanism and a lower mold mechanism, the upper mold mechanism is provided with an upper mold bottom plate and an upper mold plate, and the lower surface of the upper mold plate is provided with micro-protrusions; the lower mold mechanism is provided with a lower mold bottom plate and a lower mold plate, and the upper surface of the lower bottom plate is provided with micro-grooves, the upper mold plate and the lower mold plate are arranged opposite to each other up and down, and after the mold is closed, the micro-protrusions and micro-grooves match to form a micro-channel; the forming device is also provided with a force transmission mechanism, the force transmission mechanism is provided with a force transmission plate, a force transmission rod and a pressure edge plate, and the force transmission plate is installed with an ultrasonic vibration device; the force transmission plate is arranged between the upper mold bottom plate and the upper mold plate, and the upper mold bottom plate and the force transmission plate are connected by a hydraulic spring; a push rod is connected to the upper surface of the force transmission plate, the upper end of the push rod passes through the force transmission plate and extends out, and the force transmission plate is slidably connected to the push rod; one end of the force transmission rod is connected to the force transmission plate, and the other end of the force transmission rod passes downward through the second through hole of the upper mold plate and extends out and is connected to the pressure edge plate, the upper mold plate is slidably connected to the force transmission rod, and the pressure edge plate is arranged above the lower mold plate.

[0007] Preferably, the edge holding plate is provided with a first through hole for the micro protrusions to pass through when the mold is closed.

[0008] Preferably, the ultrasonic vibration device is provided with a vibration rod and an amplitude transformer which are connected to each other, and the vibration rod is connected to the force transmission plate.

[0009] Preferably, the forming device is further provided with a first guide column, both ends of which are respectively connected to the upper mold bottom plate and the lower mold bottom plate, and the first guide column is respectively slidably connected through the upper mold bottom plate, the force transmission plate, the upper mold plate and the lower mold plate.

[0010] Preferably, the second through hole of the upper template is a square hole, and the other end of the force transmission rod passes downward through the square hole and extends out to be connected to the edge holding plate.

[0011] Preferably, the forming device is also provided with a supporting device, which is provided with a second guide column, a guide sleeve, and a spring, the spring is installed in the guide sleeve, the upper end of the second guide column is connected to the upper template, the lower end of the second guide column is inserted into the guide sleeve and connected to the spring; the bottom of the guide sleeve is connected to the lower template.

[0012] The present invention also provides a metal bipolar plate forming method, using the metal bipolar plate forming device as described in any one of the above items.

[0013] The beneficial effects of the invention are as follows: the invention provides a metal bipolar plate forming device and method, wherein the upper mold bottom plate moves downward, driving the hydraulic spring, the force transfer plate, the force transfer rod and the edge pressure plate to move downward until they contact the surface of the plate workpiece. After the edge pressure plate contacts the plate workpiece, the upper mold bottom plate continues to move downward, compressing the hydraulic spring, and the hydraulic spring is compressed and transferred to the force transfer plate, the force transfer rod, the edge pressure plate, and finally to the plate workpiece. During the microchannel forming process, the material in the flange area yields under the action of normal stress and tensile stress, and the material flows, thereby reducing the thickness thinning of the upper fillet, side wall and lower fillet area, thereby improving the uniformity of the thickness of the entire microchannel of the metal bipolar plate, avoiding the occurrence of cracks, and optimizing the metal bipolar plate forming process, which is of great significance to promoting the industrialization development of fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0015] Figure 1 Schematic diagram of the structure of different areas of the microchannel in the bipolar plate;

[0016] Figure 2 A schematic diagram of the structure of the thickness reduction rate of different regions of the microchannel in the bipolar plate;

[0017] Figure 3 It is a structural schematic diagram of the metal bipolar plate forming device of the present invention;

[0018] Figure 4 It is a structural schematic diagram of a top view of the upper template of the present invention;

[0019] Figure 5 It is a structural schematic diagram of a three-dimensional diagram of the upper template of the present invention;

[0020] Figure 6 It is a structural schematic diagram of the edge pressing plate of the present invention;

[0021] Figure 7 for Figure 3 A schematic structural diagram of the enlarged view of part A shown.

[0022] Markings in the figure: 1. upper die bottom plate, 2. first guide column, 3. force transmission plate, 4. upper die plate, 5. lower die plate, 6. ultrasonic vibration device, 7. vibration rod, 8. amplitude rod, 9. ejector rod, 10. hydraulic spring, 11. force transmission rod, 12. edge holding plate, 13. first through hole, 16. lower die bottom plate, 17. micro protrusion, 18. micro groove, 19. sheet workpiece, 20. supporting device, 21. second guide column, 22. guide sleeve, 23. spring, 24. second through hole. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. The methods used in the invention are conventional methods unless otherwise specified; the raw materials and devices used are conventional commercial products unless otherwise specified.

[0024] like Figure 3-Figure 6 As shown, the present invention provides a metal bipolar plate forming device, which is provided with an upper mold mechanism and a lower mold mechanism. The upper mold mechanism is provided with an upper mold base plate 1 and an upper mold plate 4, and the lower surface of the upper mold plate 4 is provided with micro protrusions 17; the lower mold mechanism is provided with a lower mold base plate 16 and a lower mold plate 5, and the upper surface of the lower base plate is provided with micro grooves 18. The upper mold plate 4 and the lower mold plate 5 are arranged opposite to each other up and down, and after the mold is closed, the micro protrusions 17 and the micro grooves 18 are matched to form a micro channel.

[0025] The forming device is also provided with a force transmission mechanism, which includes a force transmission plate 3, a force transmission rod 11 and a pressure plate 12. The force transmission plate 3 is arranged between the upper mold base plate 1 and the upper mold plate 4. The upper mold base plate 1 and the force transmission plate 3 are connected by a hydraulic spring 10. The specifications of the hydraulic spring 10 can be customized according to actual conditions; a push rod 9 is connected to the upper surface of the force transmission plate 3, and the upper end of the push rod 9 passes through the force transmission plate 3 and extends out, and the force transmission plate 3 is slidably connected to the push rod 9; one end of the force transmission rod 11 is connected to the force transmission plate 3, and the other end of the force transmission rod 11 passes downward through the second through hole 24 of the upper mold plate 4 and extends out to be connected to the pressure plate 12, the upper mold plate 4 is slidably connected to the force transmission rod 11, and the pressure plate 12 is arranged above the lower mold plate 5.

[0026] When in use, the upper die bottom plate 1 and the lower die bottom plate 16 are fixed on the hydraulic press respectively, wherein the upper die bottom plate 1 is fixedly connected to the crossbeam of the hydraulic press, and the lower die bottom plate 16 is fixed on the base of the hydraulic press. The downward pressure of the upper die bottom plate 1 is controlled by controlling the displacement of the crossbeam of the hydraulic press; the sheet workpiece 19 to be formed is placed in the forming area on the lower template 5. The specific forming process is that the upper die bottom plate 1 moves downward, driving the hydraulic spring 10, the force transmission plate 3, the force transmission rod 11 and the edge pressure plate 12 to move downward until they contact the surface of the sheet workpiece 19. After the edge pressure plate 12 contacts the sheet workpiece 19, the upper die bottom plate 1 continues to move downward, compressing the hydraulic spring 10, and the hydraulic spring 10 is compressed and transmitted to the force transmission plate 3, the force transmission rod 11, the edge pressure plate 12, and finally to the sheet workpiece 19. When the upper die bottom plate 1 continues to move downward, after the lower surface of the upper die bottom plate 1 contacts the upper end of the push rod 9, the push rod 9 and the upper template 4 move downward to complete the mold closing. After forming is completed, the upper die bottom plate 1 is moved upward, driving the hydraulic spring 10, the force transfer plate 3, the force transfer rod 11 and the edge holding plate 12 to move upward, and the edge holding plate 12 drives the upper die plate 4 to move upward to realize mold opening.

[0027] The present invention uses a clamping plate 12 to apply a normal stress perpendicular to the plane to the flange area of ​​the sheet workpiece 19 before forming. According to the Mises yield criterion, applying a normal stress σ3 (i.e., an upward force perpendicular to the plate plane of the sheet workpiece 19) can reduce the yield stresses σ1 and σ2 in the other two principal stress directions (i.e., two mutually perpendicular principal stress directions in the plate plane of the sheet workpiece 19). When a sufficiently large normal stress σ3 is applied, during the microchannel forming process, the material in the flange area yields under the action of the normal stress σ3 and the tensile stresses σ1 and σ2, and the material flows, thereby reducing the thickness thinning of the upper fillet area, the sidewall area, and the lower fillet area, thereby improving the thickness uniformity of the entire microchannel of the metal bipolar plate and avoiding the occurrence of cracks.

[0028] The present invention adopts a hydraulic spring 10, and the operator can customize the parameters of the hydraulic spring 10 according to actual conditions, specifically the relationship between the compression amount and pressure of the hydraulic spring 10, thereby controlling the pressure value provided by the hydraulic spring 10 during the downward pressing process of the upper mold base plate 1. During the compression of the hydraulic spring 10, it can provide stable pressure, thereby providing stable normal stress for the edge clamp 12 to the sheet workpiece 19 during the deformation process.

[0029] In some embodiments, Figure 3 , Figure 5 , Figure 6As shown, the edge plate 12 is preferably provided with a first through hole 13 for the micro protrusion 17 to pass through when the mold is closed. The edge plate 12 is designed according to the shape of the micro channel, and the specific shape is consistent with the flange area of ​​the bipolar plate. When the mold is closed, the micro protrusion 17 of the upper mold plate 4 passes through the first through hole 13, and the corresponding area of ​​the plate workpiece 19 is pressed into the micro groove 18 of the lower mold plate 5. Finally, the upper mold plate 4 and the lower mold plate 5 are closed, and a bipolar plate micro channel is formed between the two.

[0030] In some embodiments, Figure 3 As shown, the force transmission plate 3 is preferably installed with an ultrasonic vibration device 6. During the forming process, the ultrasonic vibration device 6 is always turned on to ensure that the vibration component always maintains high-frequency resonance with the force transmission plate 3, thereby ensuring that during the pressure forming process of the sheet workpiece 19, the edge holding plate 12 and the sheet workpiece 19 are always in a high-frequency resonance state.

[0031] In some embodiments, Figure 3 As shown, the ultrasonic vibration device 6 belongs to the prior art, and is preferably provided with a vibration rod 7 and an horn 8 connected to each other, and the vibration rod 7 is connected to the force transmission plate 3. The ultrasonic vibration device 6 is controlled by a transducer and an ultrasonic generator. When in use, the ultrasonic generator is started, so that the ultrasonic wave passes through the transducer, the horn 8, and the vibration rod 7 to drive the force transmission plate 3 to move at a high frequency.

[0032] In some embodiments, Figure 3 As shown, the forming device is preferably also provided with a first guide column 2 for guiding and positioning, and the two ends of the first guide column 2 are respectively connected to the upper mold bottom plate 1 and the lower mold bottom plate 16, and the first guide column 2 is respectively slidably connected through the upper mold bottom plate 1, the force transmission plate 3, the upper mold plate 4, and the lower mold plate 5.

[0033] In some embodiments, Figure 4 As shown, the second through hole 24 opened on the upper template 4 is preferably a square hole with good stability, and the other end of the force transmission rod 11 passes through the square hole downward and extends out to be connected to the edge holding plate 12.

[0034] In some embodiments, Figure 3 , Figure 7As shown, the forming device is preferably further provided with a supporting device 20, which is installed between the upper mold plate 4 and the lower mold plate 5. The supporting device 20 is provided with a second guide post 21, a guide sleeve 22, and a spring 23, the spring 23 is installed in the guide sleeve 22, the upper end of the second guide post 21 is connected to the upper mold plate 4, the lower end of the second guide post 21 is inserted into the guide sleeve 22 and connected to the spring 23; the bottom of the guide sleeve 22 is connected to the lower mold plate 5. When the forming device is molded, part of the length of the second guide post 21 is pressed downward into the guide sleeve 22 by the upper mold plate 4, and the spring 23 is continuously compressed, and the mold is finally closed; when the forming device is molded, the upper mold plate 4 is pushed up by the second guide post 21 under the action of the elastic force of the spring 23, so that the upper mold plate 4 and the lower mold plate 5 are separated.

[0035] The present invention also provides a metal bipolar plate forming method, using the metal bipolar plate forming device as described in any one of the above items.

[0036] It should be noted that:

[0037] (1) During the edge clamping process, due to the large compressive stress, there is a large friction between the edge clamping plate 12 and the flange area of ​​the sheet workpiece 19, which makes it difficult for the material in the flange area to flow. Therefore, the present invention requires that a suitable lubricant (preferably lipid) be evenly applied to the surface of the edge clamping plate 12 and the sheet workpiece 19 before forming, and at the same time, the ultrasonic vibration device 6 is turned on to drive the force transmission plate 3, the force transmission rod 11 and the edge clamping plate 12 to vibrate at high frequency, thereby effectively reducing the friction between the edge clamping plate 12 and the sheet workpiece 19.

[0038] (2) The distance between the ejector pin 9 and the upper mold base plate 1 can be designed according to actual conditions, so that before the upper mold base plate 1 contacts the upper end of the ejector pin 9 to push the upper mold plate 4 to form, the hydraulic spring 10 can provide a sufficiently large normal compressive stress, so that during the forming process of the bipolar plate microchannel, that is, when the upper mold base plate 1 contacts the ejector pin 9 to push the upper mold plate 4 to form, the material in the bipolar plate flange area can undergo obvious plastic flow, thereby improving the uniformity of the microchannel thickness after forming.

[0039] (3) The edge clamping plate 12 is used to apply a large normal compressive stress to the flange area of ​​the upper mold plate 4, thereby promoting stress uniformity during the entire bipolar plate deformation process and effectively reducing the springback of the bipolar plate after forming.

[0040] In the description of the invention, it is necessary to understand that the terms "left", "right", "up", "down", "top", "bottom", "front", "back", "inside", "outside", "back", "middle", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the invention.

[0041] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A metal bipolar plate forming device, the forming device is provided with an upper mold mechanism and a lower mold mechanism, the upper mold mechanism is provided with an upper mold base plate (1) and an upper mold plate (4), the lower surface of the upper mold plate (4) is provided with micro protrusions (17); the lower mold mechanism is provided with a lower mold base plate (16) and a lower mold plate (5), the upper surface of the lower mold plate is provided with micro grooves (18), the upper mold plate (4) and the lower mold plate (5) are arranged opposite to each other up and down, and after the mold is closed, the micro protrusions (17) and the micro grooves (18) are matched to form a micro channel, characterized in that: The forming device is also provided with a force transmission mechanism, which is provided with a force transmission plate (3), a force transmission rod (11) and a pressure plate (12); the force transmission plate (3) is arranged between the upper mold bottom plate (1) and the upper mold plate (4); the upper mold bottom plate (1) and the force transmission plate (3) are connected by a hydraulic spring (10); the upper surface of the force transmission plate (3) is connected with a push rod (9), the upper end of the push rod (9) passes through the force transmission plate (3) and extends out, and the force transmission plate (3) is slidably connected with the push rod (9); one end of the force transmission rod (11) is connected to the force transmission plate (3), and the other end of the force transmission rod (11) passes downward through the second through hole (24) of the upper mold plate (4) and extends out to be connected to the pressure plate (12), the upper mold plate (4) is slidably connected with the force transmission rod (11), and the pressure plate (12) is arranged above the lower mold plate (5).

2. A metal bipolar plate forming device according to claim 1, characterized in that: The edge holding plate (12) is provided with a first through hole (13) for the micro protrusion (17) to pass through when the mold is closed.

3. The metal bipolar plate forming device according to claim 1, characterized in that: The force transmission plate (3) is provided with an ultrasonic vibration device (6).

4. A metal bipolar plate forming device according to claim 3, characterized in that: The ultrasonic vibration device (6) is provided with a vibration rod (7) and an amplitude transformer (8) which are connected to each other, and the vibration rod (7) is connected to the force transmission plate (3).

5. The metal bipolar plate forming device according to claim 1, characterized in that: The forming device is also provided with a first guide column (2), the two ends of which are respectively connected to the upper mold base plate (1) and the lower mold base plate (16), and the first guide column (2) is respectively slidably connected and passes through the upper mold base plate (1), the force transmission plate (3), the upper mold plate (4), and the lower mold plate (5).

6. The metal bipolar plate forming device according to claim 1, characterized in that: The second through hole (24) of the upper template (4) is a square hole, and the other end of the force transmission rod (11) passes downward through the square hole and extends out to be connected to the edge holding plate (12).

7. The metal bipolar plate forming device according to claim 1, characterized in that: The forming device is also provided with a supporting device (20), wherein the supporting device (20) is provided with a second guide column (21), a guide sleeve (22), and a spring (23), wherein the spring (23) is installed in the guide sleeve (22), wherein the upper end of the second guide column (21) is connected to the upper mold plate (4), and the lower end of the second guide column (21) is inserted into the guide sleeve (22) and connected to the spring (23); and the bottom of the guide sleeve (22) is connected to the lower mold plate (5).

8. A method for forming a metal bipolar plate, characterized in that: Use the metal bipolar plate forming device as described in any one of claims 1 to 7.

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